Nutritional liquids are well known and commercially available for a variety of nutritional or disease specific applications in infants, children and adults. These liquids are often formulated as oil-in-water emulsions comprising proteins, carbohydrates, and fats, and typically also vitamins and minerals.
These nutritional liquids have also been used to deliver variety of nutritional actives such as polyunsaturated fatty acids or fish oils. A growing body of evidence suggests that certain long chain polyunsaturated fatty acids may be beneficial for maintaining overall health, and may be useful in treating a variety of human afflictions, including cardiovascular disease, rheumatoid arthritis, depression, Alzheimer's, ulcers, cancer, hyperactivity, asthma, and similar other diseases or conditions.
Polyunsaturated fatty acids, however, often have or develop over time objectionable flavors, odors, or both, especially when formulated within a nutritional liquid. When exposed to heat and atmospheric levels of oxygen, the unsaturated structure of these polyunsaturated fatty acids reacts to form free radicals. These free radicals can continue to break down the polyunsaturated fatty acids in an auto-oxidative process, which results in the development of fishy or other undesirable flavors and odors and the eventual degradation of the beneficial polyunsaturated fatty acids.
Oxidative stability has become especially challenging when formulating a nutritional liquid containing the relatively high concentrations of polyunsaturated fatty acids often needed to obtain a therapeutic response. Allowing even some oxidation in these products often results in a highly objectionable flavor and aroma, the characteristics of which are often described as fishy, eggy, or otherwise having a rancid flavor or smell, depending upon the particular polyunsaturated fatty acid used in the formulation.
Methods of controlling the undesirable oxidation of polyunsaturated fatty acids in a nutritional product include processing or manufacturing controls to limit conditions such as elevated temperatures, exposure to ultraviolet light, exposure to oxygen and other factors that can promote oxidation. All such methods almost always include the concurrent formulation with one or more anti-oxidant additives such as ascorbic acid or ascorbyl palmitate, tocopherols, beta-carotene, or others. Although these methods are often highly effective in reducing much of the undesirable oxidation that would otherwise occur, they are often not as effective when applied to liquid nutritional compositions that contain the relatively high polyunsaturated fatty acid concentrations often needed to achieve a desired therapeutic effect.
It has now been discovered herein that certain nutritional emulsions can be formulated with little or no detectable off-flavors from high concentrations of polyunsaturated fatty acids. These emulsions are prepared by (A) heating and blending together an emulsifying agent having a melt point above about 25° C. and a non-encapsulated polyunsaturated fatty acid in a weight ratio of at least about 1:15; (B) adding the heated blend to a fat, protein, and carbohydrate mixture comprising a maltodextrin having a Dextrose Equivalent of about 10 or less, in a weight ratio of the maltodextrin to the polyunsaturated fatty acid of at least about 1:2; and (D) homogenizing, and then cooling the combination below the melt point of the emulsifying agent to form a nutritional emulsion comprising from about 0.01% to about 5% by weight of process-encapsulated polyunsaturated fatty acid.
It has also been discovered herein that these methods can be used with most any oil having hydrophobic off-notes, not just polyunsaturated fatty acids, to effectively minimize or eliminate off-notes in the final nutritional product.